The present invention relates to automotive lighting devices, and more particularly, to employing a single Light Emitting Semiconductor Device (LESD) in lighting devices for exterior automotive lighting applications.
Exterior automotive lighting, such as tail lights and brake lights, has typically been accomplished using incandescent light bulbs mounted in specifically designed lighting fixtures. Incandescent light bulbs provide a necessary light intensity required by law for use in automotive lighting applications. However, incandescent light bulbs have drawbacks. For example, incandescent light bulbs have poor power use efficiency, and a short lifetime expectancy. As an alternative to incandescent light bulbs, Light Emitting Diode (LED) lamps have also been used in tail lights and brake lights in vehicles such as, cars, motorcycles, forklifts, ATVs, trailers, and other motor vehicles. LEDs can be designed to maximize brightness and fill an entire area of a light fixture according to a desired application.
LED lamps offer advantages in comparison to incandescent light bulbs. LED lamps offer reliable performance, which represents reduced repairs, reduced maintenance, and therefore reduced costs. In addition, LED lamps promote safe motor vehicle driving due to faster turn-on times than conventional incandescent signal lamps. For example, LED lamps within a tail lamp of a vehicle increase an amount of response time available for motorists. Typical LED lamps operate approximately 0.2 seconds faster than incandescent light bulbs, which approximately results in an additional 19 feet of response time at a speed of 65 miles per hour for a trailing vehicle (i.e., distance traveled, 19 feet=(65 mile/hour)(5280 feet/mile)(1/3600 hour/sec)(0.2 sec.)).
LED lamps also consume less power than incandescent bulbs. Typically, LED lamps operate using approximately 10%-20% of an amount power consumed by incandescent light bulbs. The reduced power consumption presents both a manufacturer and vehicle owner with potential cost savings and design options such as reducing the size of an alternator, using lighter gauge wire for an automotive electrical system, or other power reduction options. In addition, LED lamps generate less heat than an incandescent bulb resulting in illuminated fixture panels that are cool-to-the-touch unlike those illuminated by incandescent lamps. A typical LED lamp provides an intense beam of colored light. The intensity and wavelength can remain stable over the LED lamps lifetime of approximately 100,000 or more hours, which is approximately 30-50 times longer than typical incandescent light bulbs.
State laws require specified light outputs for exterior automotive lighting applications, such as tail lamps. For example, in Illinois, it is required by law for automotive vehicles to possess headlights showing a white visible light discernable at a distance of at least 1000 feet, tail lamps showing a red visible light discernable at a distance of at least 500 feet, and a lamp to illuminate a rear registration plate with a white light in order to render the plate clearly legible from a distance of at least 50 feet from the rear of the vehicle. Exiting LED lamps used today employ a large amount of LEDs mounted on supports, and a corresponding number of optical arrangements mounted within the lamp, each disposed over a corresponding power source to obtain these required photometric characteristics.
In addition, typical LED light fixtures comprise numerous LEDs arranged to direct light through a light fixture. For example, a typical fixture may contain six LEDs arranged perpendicular to a lamp base in order to radiate light onto a light fixture reflector and illuminate an entire surface of the fixture. A fixture of this configuration may provide a total light output of approximately 100 Footcandles (i.e., 1 Foot candle=1 lumen/sq-ft, which is the illumination from 1 standard candle at 1 foot range). Still other existing designs may use more than 6 LEDs, and/or any number of LEDs to fulfill output requirements.
Existing solutions using LED lamps for exterior automotive lighting require a lamp design to accommodate a number of LEDs, further complicated by a heat management solution that is required to dissipate heat generated by the large number of LEDs present within a system. Such a device has thermal and packaging problems due to the large number of LEDs necessary for the required output and operation of the device. Existing LED lamps that utilize multiple LED light sources to fulfill light output requirements are difficult to manufacture due to a complexity of a light fixture design.
Consequently, an exterior automotive lighting device that has a light source that does not have these optical and thermal problems is desirable. In addition, it is desirable to provide an exterior lighting device with a structure that may be manufactured and maintained at low costs.
In view of the above, some of the problems associated with providing an exterior automotive lighting device are overcome. In one embodiment, a lighting device is provided that has a light guide and a light source that is a single Light Emitting Semiconductor Device (LESD). The single LESD is coupled to the light guide to radiate light through a first surface. The lighting device further has a control circuit is electrically coupled to the single LESD to control operation of the single LESD and a heat collector to dissipate heat generated by the single LESD and the control circuit.
In another embodiment, an exterior vehicle lamp is provided that has a lens and a reflector coupled together comprising a light guide. A single Light Emitting Semiconductor Device (LESD) is mounted within the light guide. The single LESD may be mounted within the light guide using a thermally conductive connector that is operable to dissipate heat generated by the single LESD.
In still another embodiment, a method of managing heat generated within a lighting device is provided including providing a lighting device that has a first surface and a second surface composed of a thermally conductive substrate material. The lighting device also has a single Light Emitting Semiconductor Device (LESD) operable to radiate light and a control circuit mounted between the first surface and the second surface of the lighting device electrically coupled to the single LESD to control operation of the single LESD. The method further includes providing an air channel between the first surface and the second surface of the lighting device and transferring heat generated by the single LESD and the control circuit through the air channel of the lighting device thereby uniformly distributing heat throughout the lighting device.
The lighting device of embodiments of the present invention may provide an exterior automotive lighting device that has a light source comprising a single LESD. The single LESD preferably complies with photometric requirements of automobile lighting devices. A heat management system is also provided to reduce heat flow problems present within existing automotive lighting devices.
These as well as other features and advantages of the present invention will become apparent to those of ordinary skill in the art by reading the following detailed description, with appropriate reference to the accompanying drawings.